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Porting Heads

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UTU

11-13-1998 17:14:58

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I have been following and contributing to some of the pulling posts and now I have a question.
I have been pulling my U about 6 years now And havent had it apart but I am looking to gain a little power without spending a lot more money.
When I built it I opened up the ports about as much as I safely could but I didn't do anything in the combustion chambers. I am building a new engine for my truck and have been doing some reading in hot rod books and learned about unshrouding the valves. I think this will help because my heads have a small chamber and the walls of the chamber are very close to the valves. Anyone have any suggestion on how much material to remove and how to shape the chambers? Here are the specs on my engine:
4.81 bore X 6" stroke, G rods, GE30J U LP
heads, GE31 and GE32 valves from an early
G engine, heads cut for about 12:1 compression
M670 LP intake manifold, U LP exhaust manifold, 1-5/16" carb venturi, MSD ignition and a custom ground cam. It shows about 140 hp on my dyno at about 2200 engine rpm. We run a 3000 rpm limit here but I have pulled at stock rpms and it works well also. It will spin 18.4-34s
in third gear at 5500lb, on a good track but 2nd
gear is marginal at 7500lb. I know some of you guys dont recommend high compression but mine seems to lug very well. Would it be worthwhile to tear the heads off and work on the chambers? what about the intake manifold? has
anyone tried extrusion honing these manifolds?
What are the best production manifolds for a U?
Thanks.

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Jeremy Fiorelli

11-15-1998 19:44:35

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Re: Porting Heads in reply to UTU, 11-13-1998 17:14:58

I'm not an expert on this! This is just what I have been told and have seen!!!!! From what I've seen Porting heads works very well with high RPM engines. You can gain lots of hp and increase your torque at HIGHER RPM's but the porting lowers you torque at the lower rpm�s, so I'm not sure that their would be a gain in porting heads. The porting that has been done here at the collage has all been for the high rpm engines and they have no bottom end torque. We don't necessary make the ports as big as possible we try to make the air/fuel mixture run in as striate of a line as possible and with as little turbulence ideally you should be able to look through the carb through the ports and see the top of the piston and have a mirror finish on your ports. Because their is less turbulence the air/fuel mixture doesn�t mix well but on the other hand the corners cause the air fuel mixture to separate and the rough ports slow down air flow. As for the chambers the collage made a CFM (Cubic Feet per Minute) tester to see how well their heads breath it is just a piece of pipe about the same size as their cylinders and a they use a manometer (I think you could use a vacuum gage) to check the flow of the heads I thought they should get some clear pipe about the same size of the cylinder suck air with some glitter or smoke through so you could see how the air comes into your cylinder. I never seen it work so I don't know how well it worked. It was made out of PVC pipe and a fan to suck the air through the ports.

good luck
Jeremy Fiorelli

Twin City and Minneapolis-Moline tractor and pulling

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UTU

11-17-1998 18:26:22

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Re: Re: Porting Heads in reply to Jeremy Fiorelli, 11-15-1998 19:44:35

Thanks guys, but I think I need to clarify my question a little. I already have the ports the way
I want them-opened a little and polished. My question concerns the combustion chamber
shape. The valves sit way up in the head and the chamber walls are very close to the valve pocket. I believe this is limiting flow because
when the mixture comes through the valve seat,
it has to go around the valve and runs into the side of the chamber walls. I know I need to remove some material in this area. My question is how much and how to shape it. I feel that
this engine is under fed even at low rpms and anything I can do to increase flow will help.

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Eugene VanOpdorp

11-19-1998 11:54:43

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Re: Re: Re: Porting Heads in reply to UTU, 11-17-1998 18:26:22

: Thanks guys, but I think I need to clarify my question a little. I already have the ports the way
: I want them-opened a little and polished. My : question concerns the combustion chamber
: shape. The valves sit way up in the head and the chamber walls are very close to the valve : pocket. I believe this is limiting flow because
: when the mixture comes through the valve seat,
: it has to go around the valve and runs into the side of the chamber walls. I know I need to remove some material in this area. My question : is how much and how to shape it. I feel that
: this engine is under fed even at low rpms and : anything I can do to increase flow will help.

Removal of material from combustion chamber wall
should geometrically unshrould the valve. Translated,
that means the chamber wall should be the same distance
from the valve that the valve is from the seat.
If the valve is .250 off the seat, the wall should
not be any closer than .250.More can be removed ala
big block Chevy open vs. closed combustion chamber.
Compression can be restored by milling the head if
sufficient material is there.Go slow, because it is
easier to remove iron than to replace it! Cheaper too!

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Mike

11-16-1998 13:07:08

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Re: Re: Porting Heads in reply to Jeremy Fiorelli, 11-15-1998 19:44:35

: I'm not an expert on this! This is just what I have been told and have seen!!!!! From what I've seen Porting heads works very well with high RPM engines. You can gain lots of hp and increase your torque at HIGHER RPM's but the porting lowers you torque at the lower rpm�s, so I'm not sure that their would be a gain in porting heads. The porting that has been done here at the collage has all been for the high rpm engines and they have no bottom end torque. We don't necessary make the ports as big as possible we try to make the air/fuel mixture run in as striate of a line as possible and with as little turbulence ideally you should be able to look through the carb through the ports and see the top of the piston and have a mirror finish on your ports. Because their is less turbulence the air/fuel mixture doesn�t mix well but on the other hand the corners cause the air fuel mixture to separate and the rough ports slow down air flow. As for the chambers the collage made a CFM (Cubic Feet per Minute) tester to see how well their heads breath it is just a piece of pipe about the same size as their cylinders and a they use a manometer (I think you could use a vacuum gage) to check the flow of the heads I thought they should get some clear pipe about the same size of the cylinder suck air with some glitter or smoke through so you could see how the air comes into your cylinder. I never seen it work so I don't know how well it worked. It was made out of PVC pipe and a fan to suck the air through the ports.

: good luck
: Jeremy Fiorelli

I agree. I know of at least one fellow puller who got carried away porting the head on his antique puller. It showed good HP on the dyno but fell on it's nose out on the track. Oh well, that head makes a nice door-stop now.

Antique Tractor Pulling

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